Field of the Invention
The present invention relates to a structure of a toroidal continuously variable transmission for use in, for example, an electric power generating device for an aircraft.
Description of Related Art
As an electric power generating device for an aircraft, it is known to use a constant frequency generator (IDG) that operates while keeping a rotation rate (frequency) of a generator constant even when a rotation rate of an aircraft engine, which is a drive source, varies. As a transmission for keeping a rotation rate of the generator constant in the IDG, a toroidal continuously variable transmission has been proposed. The toroidal continuously variable transmission includes a toroidal transmission unit that includes: an input disc and an output disc concentrically arranged so as to be opposed to each other; and a power roller that is brought into contact with opposed curved concave surfaces of both discs at high pressure. By adjusting a tilt angle of the power roller relative to both discs, it is possible to steplessly (continuously) vary a gear ratio.
In general, as a toroidal continuously variable transmission, a double-cavity-type is adopted in which the two toroidal transmission units are arranged coaxially. As a double-cavity-type toroidal continuously variable transmission, a transmission in which two discs of two toroidal transmission units which two discs are adjacent to each other at an axially central portion are integrally formed (see, e.g., Patent Document 1) and a transmission in which such two discs are formed as separate members (see, e.g., Patent Document 2) are known. In the disc-integrated-type transmission, deformation, in the axial direction, of the two discs arranged at the axially central portion is small, and the entire transmission can be configured with a small size and a light weight. Meanwhile, in the disc-separate-type transmission, since a gear for input and output can be disposed between the discs adjacent to each other at the axially central portion, the outer diameter of the gear can be reduced to suppress an increase in the circumferential speed of the gear.